U.S. Pat. No. 4,569,109 Fetouh, assigned to the assignee of the present invention, extensively describes prior methods of making split bearing assemblies for various uses. Examples of such uses are for engine crankshaft main and connecting rod bearing assemblies, camshaft bearing assemblies, crank-supporting bearing assemblies for compressors, presses and other machines, and other rotatable shaft-supporting bearing assemblies, in all of which a removable saddle-like bearing cap is secured to a mating saddle-like main body to provide for the installation and removal of a rotatable shaft, an attached connecting rod, or another device.
U.S. Pat. No. 4,569,109 further refers to prior methods of forming the main body and cap as integral members and completely machining all necessary surfaces, including the journal encircling opening or bore, before separating the main body and cap members techniques which involve fracturing the components along predetermined fracture planes, leaving interlocking rough surfaces that are capable of being re-engaged for assembly of the components into an operating assembly.
The prior art fracture techniques are said to include various methods of weakening the separation planes, such as by drilling holes therein and/or providing weakening notches along one or more edges. Embrittlement of the material in the separating planes may also be provided for either by material selection, heat treatment (including hardening of various types), or by freezing the material to reduce its temperature below the embrittlement point.
Further, U.S. Pat. No. 4,569,109 suggests that the various types of prior fracture techniques introduce various problems, among which are reduction of the engageable surface area of the separated parts that reduces the allowable clamping load and, in some cases, the introduction of excessive bending of the separating parts which results in yielding deformation of metal along the edges that interferes with proper reassembly of the separated components. Deformation of the previously machined opening can also be a problem with some methods.
U.S. Pat. No. 4,569,109 proposes a two step fracture separation method which avoids deformation of the fractured material at the edge of the last-broken legs of the bearing assembly. This method includes, first, fracturing one of the pairs of integrally formed legs and, then, restraining the fractured legs from moving substantially away from their mated positions, by clamping or the like, while fracturing the other pair of integrally formed legs. The fracture steps are accomplished in each instance by placing the split planes in tension, such as by applying a separating force in the bore between the cap and body.